System and method for water disinfection

ABSTRACT

The efficiency of water disinfection can be significantly increased by supplying the ozone in combination with oxygen to an inlet of a cavitation pump. The ozone and the oxygen are turned into ultra-fine bubbles via cavitation action within the pump, facilitating the dissolution of the oxygen and ozone within the water. The water mixed with the oxygen and the ozone is subsequently supplied to a line atomizer, where the dissolution of the ozone within the mixture is completed. The combined use of the cavitation pump and the line atomizer can lead to a substantially complete dissolution of the supplied ozone within water that needs to be disinfected, allowing to easily achieve the concentration of ozone necessary for water disinfection. Due to this efficiency, the system and method described are highly scalable and suitable for water purification at water purification plants of various sizes.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is a continuation of U.S. Pat. No. 10,287,194,issued May 15, 2019, the disclosure of which is incorporated byreference.

FIELD

The present invention relates in general to water purification, and inparticular, to a system and method for gas-based water disinfection.

BACKGROUND

Access to safe drinking water has been described by the World HealthOrganization as a basic human right that is essential to health. Whilethere are many sources from which fresh water could be obtained, such asgroundwater, upland lakes and reservoirs, and rivers, such water may notbe suitable for drinking due to presence of various microorganisms inthe water. The microorganism contamination can pose immediate healthrisks, such as when the water is contaminated with pathogenic strains ofE. Coli bacteria, cholera causing Vibrio cholera, viruses, and protozoanparasites, such as Giardia lamblia. Making the water suitable fordrinking requires disinfection, preferably to the point ofsterilization. As the size of the population requiring the drinkingwater, and consequently the volume of drinking water needed, grows, thechallenge of purifying the water to a sufficient extent to make thewater suitable for drinking similarly becomes larger.

Several techniques are currently in use for disinfection of water, butthese techniques have significant drawbacks. For example, addition ofchemicals, such as chlorine-containing compounds, have only limitedeffectiveness against pathogenic protozoa such as Giardia lamblia.Likewise, while disinfecting water with ultraviolet light is effectivein low turbidity water, the effectiveness decreases as the turbidityincreases.

Disinfection using ozone, which can act as a strong oxidizing agent thatis toxic to most water-borne microorganisms, provides an effectivealternative to chemical-based and ultraviolet-light based watersterilization. Ozone is created by passing oxygen through an ultravioletlight or a cold electrical discharge and is added to the water by bubblecontact.

A concentration of 1-3 ppm within the water being purified is generallyrequired for the ozone to be an effective disinfecting agent, with ahigher concentration being potentially damaging to the pipes carryingthe ozonated water. Introducing ozone into the water in thatconcentration may be a challenge that requires significant resources andthat current techniques are not efficient at handling, especially inindustrial settings, such as when the ozonation has to be performed at awater treatment plan responsible for providing drinking water to a largecity. For example, a bubble diffuser is a device for dissolving ozoneinto water in which a porous object is used to break ozone gas intosmall bubbles at the bottom of a water basin with the bubbles slowlyrising to the top of the basin and partially dissolving in the water.However, the efficiency with which a bubble diffuser dissolves ozonetends not to exceed 75%, with the at least 25% inefficiency making thepurification unnecessarily expensive and wasteful, especially as highervolumes of water are processed. While the efficiency may be improved byincreasing the depth of the water basin, such an increase may not becommercially viable nor technically practicable in a industrialapplication.

Accordingly, there is a need for a way to perform efficient waterpurification using ozone that is also scalable for industrial-scalewater disinfection.

SUMMARY

The efficiency of water disinfection can be significantly increased bysupplying the ozone in combination with oxygen to an inlet of acavitation pump, The ozone and the oxygen are turned into ultra-finebubbles via cavitation action within the pump, facilitating thedissolution of the oxygen and ozone within the water. The water mixedwith the oxygen and the ozone is subsequently supplied to a lineatomizer, where the dissolution of the ozone within the mixture iscompleted. The combined use of the cavitation pump and the line atomizercan lead to a substantially complete dissolution of the supplied ozonewithin water that needs to be disinfected, allowing to easily achievethe concentration of ozone necessary for water disinfection. Due to thisefficiency, the system and method described are highly scalable andsuitable for water purification at water purification plants of varioussizes.

In one embodiment, a system and method for liquid disinfection isprovided. Through one or more pipes a liquid contaminated bymicroorganisms is pumped to a cavitation device. Using a gas generator agas mixture is generated, the gas mixture including a plurality ofgases. The gas mixture is pumped into one or more of the pipes, whereinthe gas mixture mixes with the liquid within one or more of the pipes.The cavitation device dissolves a portion of the gas mixture within theliquid via cavitation and the liquid and the remaining undissolved gasmixture are pumped into a line atomizer. A further portion of the gasmixture is dissolved by the line atomizer into the liquid, wherein thedissolved gases reduce a concentration of microorganisms within theliquid.

Still other embodiments of the present invention will become readilyapparent to those skilled in the art from the following detaileddescription, wherein is described embodiments of the invention by way ofillustrating the best mode contemplated for carrying out the invention.As will be realized, the invention is capable of other and differentembodiments and its several details are capable of modifications invarious obvious respects, all without departing from the spirit and thescope of the present invention. Accordingly, the drawings and detaileddescription are to be regarded as illustrative in nature and not asrestrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a system for gas-based watersterilization in accordance with one embodiment.

FIG. 2 is a flow diagram showing a method for gas-based waterdisinfection in accordance with one embodiment.

DETAILED DESCRIPTION

By introducing a gaseous mixture that includes ozone and oxygen to aninlet of a cavitation pump that is interfaced to a line atomizer, theefficiency of dissolution of the ozone and the oxygen within water, andconsequently the degree of water disinfection can be significantlyincreased. FIG. 1 is a block diagram showing a system 10 for gas-basedwater sterilization in accordance with one embodiment. The system 10 canbe implemented in a water purification plant, though other kinds ofimplementations are possible.

The system 10 includes a flow meter 12 through which water 11 that needsto be purified flows. The flow meter 12 measures the rate at which thewater 11 flows, though other kinds of measurements by the flow meter 12.In one embodiment, the water 11 in need of purification can begreywater, water that has been generated in households or officebuildings from streams without fecal contamination, such as from sinks,showers, baths, washing machines and dish washing machines. In a furtherembodiment, the water 11 may come from other sources. The water may bestored on the same site as the flow meter 12, or delivered from anotherlocation, and be supplied to the flow meter 12 via one or more pipes(not shown). Regardless of the source, the water 11 needs to besubstantially free of solid sediments prior to passing through the flowmeter 12.

The flow meter 12 is also connected via one or more pipes 13 to acavitation pump 14, with water 11 that has been analyzed by the flowmeter 12 flowing through the pipes 13 to the cavitation pump 14. Alsoconnected to the one or more pipes 13 is a gas generator 15. The gasgenerator generates a gas mixture 16 of oxygen and ozone, such bypassing oxygen through an ultraviolet light, though other ways togenerate the mixture 16 are possible. In one embodiment, the mixture iscomposed of about 80% oxygen and about 20% of ozone, though other ratiosof oxygen and ozone in the mixture 16 are possible. The gas mixture 16is pumped through one or more gas supply pipes 17 to one or more of thepipes 13, mixing with the water 11 prior to the water reaching thecavitation pump 14. The amount of the gas mixture pumped by the gasgenerator 15 can depend on the flow rate of the water 15 measured by theflow meter 12. In one embodiment, the flow rate can vary from 120 m³ ofwater 11 per hour to 2,000 m³ of water 11 per hour, and the rate (andconsequently the amount) of the gas mixture 16 would increaseproportionally with the increase in flow rate (and thus the amount ofwater 11 being treated). As further described below, the amount of thegas mixture can further be increased if the quality of the purificationof the water 11 proves to be below a desired level. The settings of thegas generator 15 regulating the rate at which the gas mixture 16 ispumped via the gas supply pumps 17 can be changed either manually, suchas by personnel of a water purification plant, or under computerizedcontrol that allows automatic (or under remote user control) changing ofthe settings of the gas generator 15. In one embodiment, the volume ofthe gas mixture 16 that enters the cavitation pump 14 does not exceed15% of the total volume of the water 11 and the mixture 16 within thecavitation pump. In a further embodiment, another ratio of the volume ofthe water 11 to the volume of the gas mixture 16 could be used. Whileproviding the ozone as part of the mixture 16 is essential for thesterilization of the water, the presence of dissolved oxygen in thewater 11 further prevents growth of anaerobic pathogenic microorganisms.

Cavitation is the formation of vapor cavities in a liquid. In pumps,cavitation is caused by an impeller of the pump moving through a liquid,with low-pressure areas being formed as the liquid accelerates and movespast the blades, causing the liquid to vaporize and form small bubblesof gas. While cavitation in most cases is undesirable as damaging to thecomponents of the pump, the cavitation pump 14, while subject to theincreased wear due to cavitation, takes advantage of the cavitationeffect to help dissolve the gaseous mixture within the 16 within thewater 11. In particular, the rotation of the impeller of the cavitationpump 14 is fast enough to slice the formed bubbles into multiple smallerbubbles, thus forming ultra-fine bubbles 22 (of a diameter from 1nm-30,000 nm). Upon the formation of the bubbles, a portion of the ozoneand a portion of oxygen in the gaseous mixture rapidly dissolve withinthe water 11 causing the destruction of the microorganisms or othermolecules present in the water 11.

The cavitation pump 14 operates under a high pressure, which facilitatesthe dissolution of the ozone (and the oxygen) within the water 11. Inone embodiment, the pressure inside the pump 14 is between 0.0981 MPaand 5.394 MPa, though other values of pressure are also possible.

The vapor-liquid mixture 18 of water 11 (with dissolved ozone andpartially dissolved oxygen), gaseous ozone and oxygen, and theultra-fine bubbles 22 within the water 11 is pumped by the cavitationpump 14 via one or more pipes 19 to a line atomizer 20 that completesthe dissolution of the ozone within the water 11 by churning and mixingthe vapor-liquid mixture 18 under high pressure (approximately0.0981-5.394 MPa (1-55 kg/cm²), with the dissolution of the ozone andthe oxygen being accelerated due to the tornado effect within the lineatomizer 2-. In one embodiment, the line atomizer 20 can be the OHRMixersold by OHR Laboratory Corporation of 536-1, Noda, Irumashi, Saitama358-0054 Japan. In a further embodiment, other line atomizers 20 can beused. In one embodiment, about 40% of the ozone pumped by the cavitationpump 14 into the water 11 is dissolved at the cavitation pump 14, withthe remaining amount of ozone (about 60%) being dissolved in the water11 in the line atomizer 20. Other amounts of ozone dissolved within thecavitation pump 14 and the line atomizer 20 are possible. While completedissolution of the provided ozone within the water 11 is possiblefollowing the processing by the line atomizer 20, in one embodiment,about 70%-80% of the oxygen dissolves within the water 11. In a furtherembodiment, other percentage of oxygen dissolution is possible.

The combination of the cavitation pump 14 and the line atomizer 20 allowfor substantially complete dissolution of the ozone within the water 11,allowing to achieve the desired concentration of ozone (1-3 ppm) withminimal amount of ozone expended. Thus, despite the inefficienciescaused by the cavitation in the cavitation pump, overall, introducingthe gas mixture 16 at the inlet of the cavitation pump 14, with thesubsequent processing by the line atomizer 20, increases the overallefficiency of the ozone dissolution and decreases the amount ofresources necessary to disinfect the water 11 to a desired degree,including to a degree of sterilization. The efficiency is greater thanin alternative solutions involving line atomizers, such as when two lineatomizers are connected in a series without the use of a cavitationpump. Further, due to the high efficiency, the system 10 is easilyscalable and can be adapted to process at water purification plans ofdifferent sizes.

The water 21 that is discharged from the line atomizer 20 can beanalyzed to make sure that the sterilization effect of ozone isadequate. Such processing can include testing of the concentration ofmicroorganisms within the water 21 (such as determining optical densityof the microorganism) and determining other kinds of microorganismswithin the ozonated water 21. Other kinds of tests are possible. In oneembodiment, the testing can be done three times a day, though in afurther embodiment, other kinds of schedule for the testing is possible.In one embodiment, the testing can be done by humans; in a furtherembodiment, the testing can be automated, such as using sensorspositioned to analyze the disinfected water 21. Based on the analysis,the settings of the gas generator 15 can be changed to increase the rateat which the gas mixture 16 is pumped from the gas generator 16 (andthus increasing the concentration of the ozone in the water 11).

The components of the system 10 can be operated manually or under acontrol of a computer. Thus, a computer (not shown) can be interfaced(wirelessly or through wired connections) to the gas generator 15, theflow meter 12, any other sensors in the system 10, and control theamount of the gas mixture 16 pumped by the gas generator based on theflow rate of the water 11 or the determined characteristics of thedisinfected water 21, either automatically or under local or remote usercontrol.

FIG. 2 is a flow diagram showing a method 30 for gas-based waterdisinfection in accordance with one embodiment. Flow of water 11 inpipes leading to the cavitation pump 14 is measured using a flow meter12 (step 31). The settings of the gas generator 15, such as the rate atwhich the gas generator pumps the gaseous mixture 16 is pumps via thepipes 17, is determined based on the measured flow rate, and thegenerator 15 is set to run at the determined settings (step 32). The gasgenerator 15 supplies the gas mixture through the one or more pipes 17into the one or more pipes 13, where the gas mixture 16 mixes with thewater 11 (step 33) and from where the gas mixture 16 and the water 11are pumped into the cavitation pump 14 (where the gas mixture ispartially dissolved within the water via cavitation created by theoperation of the pump 14) (step 34). The cavitation pump 14 furtherpumps the vapor-liquid mixture 18 of water 11 (with partially dissolvedozone and oxygen), gaseous ozone and oxygen, and ultra-fine bubbles 22created via the cavitation to the line atomizer 20, where the ozone andthe oxygen are further dissolved within the water 11, causing thedisinfection of the water (step 35). Optionally, the disinfected water21 extruded from the line atomizer 20 is analyzed, such by testing thedensity and kinds of microorganisms present within the disinfected water21, though other kinds of analysis are possible (step 36). If theresults of the analysis are satisfactory (such as with the density ofthe microorganisms being below a predefined threshold or absence ofcertain pathogenic microorganisms) (step 37), the method moves to step39. If the results are not satisfactory (step 37), the settings of thegas generator 15 are modified, such as by increasing the rate at whichthe gas mixture 16 is supplied via the one or more supply pipes (step38), with the method 30 returning to step 33.

If more unpurified water 11 remains (step 39), the method 30 returns tostep 31. If no more unpurified water remains to be processed (step 39),the method 30 ends.

While the description above refers to disinfection of water, in afurther embodiment, the system 10 and method 30 described above could beused for disinfection of another liquid.

While the invention has been particularly shown and described asreferenced to the embodiments thereof, those skilled in the art willunderstand that the foregoing and other changes in form and detail maybe made therein without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A system for liquid disinfection, comprising: oneor more pipes through which a liquid contaminated by microorganisms issupplied to a cavitation pump; a gas generator configured to generate agas mixture comprising a plurality of gases and to pump the gas mixtureinto one or more of the pipes, wherein the gas mixture mixes with theliquid within one or more of the pipes; a cavitation pump configured toprovide cavitation by an impeller of the pump under a pressure ofsubstantially 0.0981 MPa-5.394 MPa and to cause a formation in theliquid of ultra-fine bubbles via the impeller slicing larger bubblesinto the ultra-fine bubbles, to dissolve a portion of the gas mixturewithin the liquid via the cavitation, and to pump the liquid, theultra-fine bubbles within the liquid, and the remaining undissolved gasmixture into a line atomizer; and the line atomizer configured todissolve a further portion of the gas mixture into the liquid bychurning and mixing the liquid, the ultra-fine bubbles, and the gasmixture under the pressure of substantially 0.0981 MPa-5.394 MPa,wherein the dissolved gases reduce a concentration of microorganismswithin the liquid.
 2. The system according to claim 1, wherein theliquid comprises greywater.
 3. The system according to claim 2, whereinthe gas generator generates the gas mixture by passing one of the gasesthrough ultraviolet light.
 4. The system according to claim 1, furthercomprising: one or more sensors positioned to analyze the liquidfollowing the dissolution of the further portion of the gas mixture bythe line atomizer.
 5. The system according to claim 4, wherein theanalysis comprises determining one or more of an optical density of themicroorganisms within the liquid and determining kinds of themicroorganisms within the liquid.
 6. The system according to claim 4,further comprising: a flow meter configured to measure a flow rate ofthe liquid through one or more of the pipes.
 7. The system according toclaim 6, further comprising: a computer interfaced to the gas generator,the flow meter, and the one or more sensors, and configured to controlan amount of the gas mixture pumped by the gas generator into the one ormore pipes based on one or more of the flow rate and the analysis by thesensors.
 8. The system according to claim 7, wherein the computer isconfigured to control the amount of the gas mixture at least one ofautomatically and under a control of a user.
 9. A method for liquiddisinfection, comprising: pumping through one or more pipes a liquidcontaminated by microorganisms to a cavitation pump; generating using agas generator a gas mixture comprising a plurality of gases and pumpingthe gas mixture into one or more of the pipes, wherein the gas mixturemixes with the liquid within one or more of the pipes; dissolving undera pressure of substantially 0.0981 MPa-5.394 MPa by the cavitation pumpa portion of the gas mixture within the liquid via cavitation producedby an impeller of the pump, causing a formation of ultra-fine bubbles inthe liquid via the impeller slicing larger bubbles into the ultra-finebubbles, and pumping the liquid, the ultra-fine bubbles within theliquid, and the remaining undissolved gas mixture into a line atomizer;dissolving by the line atomizer a further portion of the gas mixtureinto the liquid by churning and mixing the liquid, the ultra-finebubbles, and the gas mixture under a the pressure of substantially0.0981 MPa-5.394 MPa, wherein the dissolved gases reduce a concentrationof microorganisms within the liquid.
 10. The method according to claim9, wherein the liquid comprises greywater.
 11. The method according toclaim 10, further comprising: generating by the gas generator the gasmixture by passing one of the gases through ultraviolet light.
 12. Themethod according to claim 9, further comprising: analyzing using one ormore sensors the liquid following the dissolution of the further portionof the gas mixture by the line atomizer.
 13. The method according toclaim 12, wherein the analysis comprises determining one or more of anoptical density of the microorganisms within the liquid and determiningkinds of the microorganisms within the liquid.
 14. The method accordingto claim 12, further comprising: measuring by a flow meter a flow rateof the liquid through one or more of the pipes.
 15. The method accordingto claim 14, further comprising: interfacing a computer to the gasgenerator, the flow meter, and the one or more sensors, and controllingan amount of the gas mixture pumped by the gas generator into the one ormore pipes based on one or more of the flow rate and the analysis by thesensors.
 16. The method according to claim 15, wherein the computer isconfigured to control the amount of the gas mixture at least one ofautomatically and under a control of a user.